refactor(dedup): TryMatchTwoCharOperator helper in PG StatementReader

The PostgreSql-specific operator dispatch in
`StatementReader.TryHandleAdditionalCharacter` had four similar 4-7
line blocks (each handling a single-char operator with one or more
two-char variants — \<, \>, \|, \=). Sonar flagged it as a
self-duplication.

Extract a small `TryMatchTwoCharOperator(char, string)` helper that
encapsulates the "if next char matches, advance and emit two-char
operator" pattern. Each operator handler now reads as a small list:

    if (CurrentCharacter == '<')
    {
        MovePosition();
        if (TryMatchTwoCharOperator('=', "<=")) return true;
        if (TryMatchTwoCharOperator('>', "<>")) return true;
        if (TryMatchTwoCharOperator('<', "<<")) return true;
        _currentToken = new Token(TokenType.Operator, "<");
        return true;
    }

Reverses my earlier "extracting would obscure intent" call after
re-reading — the helper-based form actually surfaces the intent
("two-char operator dispatch") more clearly than the original.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Strata.SqlTools.PostgreSql/Statements/StatementReader.cs

@@ -104,76 +104,39 @@ public class StatementReader : SqlServerStatementReader
 
         if (CurrentCharacter == '=')
         {
-            // Handle => operator (used in PostgreSQL for hstore and other operations)
+            // =, => (PostgreSQL hstore + other operations)
             MovePosition();
-            if (CurrentCharacter == '>')
+            if (TryMatchTwoCharOperator('>', "=>")) return true;
-            {
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, "=>");
-                return true;
-            }
-            // Single = is handled as regular operator
             _currentToken = new Token(TokenType.Operator, "=");
             return true;
         }
 
         if (CurrentCharacter == '|')
         {
-            // Handle || concatenation operator
+            // |, ||
             MovePosition();
-            if (CurrentCharacter == '|')
+            if (TryMatchTwoCharOperator('|', "||")) return true;
-            {
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, "||");
-                return true;
-            }
-            // Single | is also an operator
             _currentToken = new Token(TokenType.Operator, "|");
             return true;
         }
 
         if (CurrentCharacter == '<')
         {
-            // Handle <, <=, <>, << operators
+            // <, <=, <>, <<
             MovePosition();
-            if (CurrentCharacter == '=')
+            if (TryMatchTwoCharOperator('=', "<=")) return true;
-            {
+            if (TryMatchTwoCharOperator('>', "<>")) return true;
-                MovePosition();
+            if (TryMatchTwoCharOperator('<', "<<")) return true;
-                _currentToken = new Token(TokenType.Operator, "<=");
-                return true;
-            }
-            if (CurrentCharacter == '>')
-            {
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, "<>");
-                return true;
-            }
-            if (CurrentCharacter == '<')
-            {
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, "<<");
-                return true;
-            }
             _currentToken = new Token(TokenType.Operator, "<");
             return true;
         }
 
         if (CurrentCharacter == '>')
         {
-            // Handle >, >=, >> operators
+            // >, >=, >>
             MovePosition();
-            if (CurrentCharacter == '=')
+            if (TryMatchTwoCharOperator('=', ">=")) return true;
-            {
+            if (TryMatchTwoCharOperator('>', ">>")) return true;
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, ">=");
-                return true;
-            }
-            if (CurrentCharacter == '>')
-            {
-                MovePosition();
-                _currentToken = new Token(TokenType.Operator, ">>");
-                return true;
-            }
             _currentToken = new Token(TokenType.Operator, ">");
             return true;
         }
@@ -244,6 +207,23 @@ public class StatementReader : SqlServerStatementReader
 
         return stringValue.ToString();
     }
+
+    /// <summary>
+    /// If the position is currently sitting on <paramref name="nextChar"/>, advances past it,
+    /// emits <paramref name="twoCharOperator"/> as the current Operator token, and returns
+    /// <c>true</c>. Otherwise leaves position untouched and returns <c>false</c>. Used by the
+    /// multi-character operator dispatch (e.g. <c>&lt;</c>/<c>&lt;=</c>/<c>&lt;&gt;</c>/<c>&lt;&lt;</c>).
+    /// </summary>
+    private bool TryMatchTwoCharOperator(char nextChar, string twoCharOperator)
+    {
+        if (CurrentCharacter != nextChar)
+        {
+            return false;
+        }
+        MovePosition();
+        _currentToken = new Token(TokenType.Operator, twoCharOperator);
+        return true;
+    }
 }